Have you heard the news from this article? None of it was new to me, but it reinforced the idea that I should not carry a cell phone on my body. http://www.nytimes.com/2010/11/14/business/14digi.html?_r=2

Having said that, I do sometimes clip the phone onto my pants or put it in a rear pocket. I don't use my phone that much though and really only have it for emergency purposes.